1. Field of the Invention
This invention relates to a digital camera capable of electronic zoom processing, and to a method of controlling the operation of the camera.
2. Description of the Related Art
In a portable image pick-up apparatus such as a digital camera, a subject is imaged by a solid-state electronic image sensing device such as a CCD. An image having a high resolution is obtained by providing the solid-state electronic image sensing device with a large number of pixels.
Some digital cameras are provided with a display device, and shooting angle is decided while the image of the subject is displayed on the display device. The resolution of the display device provided on the digital camera is not high and is in general lower than that of the solid-state electronic image sensing device.
In order to image a subject at a fixed period of {fraction (1/60)} of a second using a solid-state electronic image sensing device and display the image of the subject, which is represented by a video signal obtained by such imaging, smoothly in the form of a movie on a display device provided on a digital camera, it is required that the number of lines in the vertical direction of the image represented by the video signal output from the solid-state electronic image sensing device approximate the number of lines of the display device. In order to achieve this, the device is driven in such a manner that signal charge, which has accumulated in the photoelectric transducers constituting the solid-state electronic image sensing device, will be read out at intervals of a plurality of lines, by way of example. This is referred to as “pixel downsampling”.
Digital cameras capable of electronic zooming also have come into widespread use. By applying a zoom command, the image of a subject within a prescribed area is enlarged by interpolating pixels.
When pixels are downsampled in order to display a moving image on the display device, resolution declines. If such an image is subjected to electronic zoom processing, often the image undergoes a further decline in resolution.